Lights out: Earth Hour around the globe

Protest by candlelight: The lights went out all over the world on Saturday as campaigners from the Great Pyramids to the Acropolis and the London Eye to the Las Vegas strip pressed the 'off' switch to mark the second Earth Hour. Nearly 4,000 cities and towns in 88 countries planned to join in the World Wildlife Fund-sponsored event, a time-zone-by-time-zone plan to dim non-essential lights between 8.30pm and 9.30pm local time Photograph: Manish Swarup/AP

The Sydney skyline is darkened after thousands of lights were turned off. Landmark buildings and homes went dark for an hour to highlight the threat of climate change Photograph: Patrick Riviere/Reuters

Cyclists generate enough energy with pedal power to supply the electricity for an open-air concert in Melbourne. The Future Spark project ran from 23 March and finished as Earth Hour ended Photograph: Rob Griffith/AP

Kaleidoscopic colours from glow-sticks brighten the night in Manila Photograph: Pat Roque/AP

Before and after at Beijing's National Grand theatre Photograph: Jason Lee/REUTERS

Downtown Shanghai lights up after Earth Hour Photograph: ChinaFotoPress/Getty Images

Burning candles make up the message 'Vote Earth' in Singapore Photograph: How Hwee Young/EPA

Singapore's financial district, normally a blaze of light and colour at night, dims down Photograph: Pablo Sanchez/Reuters

Having fun with a serious message: Students dressed as a polar bear and a gorilla — two species under serious threat from global warming — get ready for lights-out in Gothenburg, Denmark. A UN-led conference in the Danish capital of Copenhagen later this year is meant to approve a new global warming treaty post-2012, when the Kyoto protocol expires Photograph: Erik Abel/AFP/Getty Images

A fire acrobat performs to mark WWF's Earth Hour in front of the National Theatre in Sofia Photograph: Dimitar Dilkoff/AFP/Getty Images

Millenium bridge in Newcastle Photograph: Nigel Roddis/REUTERS

Paris's most famous landmark is all but invisible against the night sky Photograph: Horacio Villalobos/EPA

London Photograph: Lefteris Pitarakis/AP

New York Photograph: Timothy A. Clary/AFP/Getty Images

Even Las Vegas, not known for environmental concern, took part Photograph: Steve Marcus/Reuters

Cartagena de Indias in Colombia Photograph: Ricardo Maldonado/EPA

Josefina Castro cups a candle during the Earth Hour blackout in Guatemala City Photograph: Ulises Rodriguez/EPA